Abstract
Age-hardening mechanisrn in a 16K and 14K gold commercial dental alloys was studied by means of electron microscopic observations, electron and X-ray diffraction studies. Metastable AuCu I' phase and equilibrium AuCu I phase were formed by ageing in both alloys. The hardening was due to the introduction of coherency strain at the interface between the AuCu I' ordered platelets and the matrix. The equilibrium AuCu I ordered phase associated with the α2 phase was formed predominantly at the grain boundaries as lamellar structure and they did not contribute to the age-hardening.
